The present invention relates in general to electrical impedance tomography, and in particular to a new and useful method and apparatus for the adaptive selection and application of optimal current patterns for use in electric current computed tomography (ECCT) to reconstruct the best image.
An apparatus for practicing electric current tomography comprising 32 electrodes and a plurality of current generators is disclosed in an article by the coinventors of the present invention, entitled "An Electric Current Tomograph", IEEE TRANSACTIONS 0N BIOMEDICAL ENGINEERING, Vol. 35, No. 10, October 1988.
A process and apparatus for utilizing a similar array of electrodes in computed tomography is disclosed in U.S. Pat. No. 4,920,490 granted to one of the coinventors of the present invention. U.S. Pat. No. 4,920,490 is incorporated here by reference and discloses a means for distinguishing one conductivity from another. It does not disclose an adaptive process which creates the best current patterns and then uses these current patterns iteratively to reconstruct the best image.
ECCT is used to determine electrical impedance distribution within a body from electrical measurements made on the surface of the body. It has a wide range of possible applications in medical imaging, geology and mineral exploration, in the nondestructive evaluation of solid materials, and in the control of manufacturing processes.
When many electrodes are used to make the electrical measurements at the surface of the body, as in the foregoing references, many different current patterns can be utilized. The present invention as will be explained later in this disclosure, involves a new process for determining all of the current patterns to be used, and a related process for making an image of the internal impedance distribution.
Other approaches to the selection of current patterns are disclosed in U.S. Pat. No. 4,486,835 to Bai, et al. and U.S. Pat. No. 4,539,640 to Fry, et al. Neither of these references, however, disclose the adaptive selection of optimal current patterns as in the present invention.